The Y-wing is the last of the Rebel Alliance fighters currently available (though I certainly look forward to the B-wing release later this autumn!).
Being maneuverable like a drifting log and slow like a drugged Sloth - the Y-wing makes up for this by having the most durable hull and shield integrity among the Rebel fighters. The combined hit points amount to an impressive 8! Compare this to the 5 of an X-wing and 4 of an A-wing and you understand that this is one durable fighter.
The Y-wing also has a very good upgrade, the Ion cannon turret, which has a 360degree line of sight and is great for temporarily disabling enemy fighters. You can only ever inflict 1 damage with it, but a hit results in the enemy ship only being able to move "1 forward" as its next activation. This can be devastating in combination with a supporting fighter - but I suppose (and have read about such a thing) that you could field the Y-wings en masse and slowly cruise around the table disabling ships left and right.
Check my blog for the full overview of the blister contents and more info:
http://anatolisgameroom.blogspot.se/2013/06/star-wars-x-wing-y-wing-expansion-pack.html